The present invention relates to a method for making aromatic polyformals. More particularly, the present invention relates to a method for eliminating cyclic polyformal from film forming aromatic polyformal.
As shown in copending application of Allan S. Hay, Ser. No. 889,393, now abandoned, filed concurrently herewith and assigned to the same assignee as the present invention, aromatic polyformal consisting essentially of chemically combined units of the formula, EQU --OROCH.sub.2 --, (1)
is made by reacting a bisphenol, methylene halide, alkali metal hydroxide in combination with a dipolar aprotic solvent, or in an organic solvent utilizing a phase transfer catalyst, where R is a C.sub.(6-30) divalent aromatic radical defined more particularly below. It has been found that in the process of forming and recovering such aromatic polyformal from the aforementioned reaction mixture, the aromatic polyformal often has a substantial percent by weight aromatic polyformal in the cyclic state. In particular instances, the utility of films derived from the film forming aromatic polyformal can be reduced as a result of the presence of cyclic aromatic polyformal; the films can be hazy and have a reduced Notched Izod Impact value.